Yes you have to use the indexed parameters — the firmware was built up from an early version when OS was based on ATmega328 mcu with only 32KB flash and 2KB ram. As a result, a lot of the design decisions have to be centered around optimizing the code size. So the option parameters were not parsed using human readable names but rather indices. If we had OS 3.0 hardware to begin with, it would have been quite a bit easier without so much low-level optimizations.